The present invention relates to a fastening arrangement for axially securing machine elements and has particular application to installing rolling bearings without clearance or preloaded on a shaft or the like and a method for assembly thereof.
A known process for producing such an arrangement is illustrated in German preliminary application No. 2,204,831. In accordance with the teachings of this prior invention, the preloading is applied exclusively to the machine element to be fastened by means of a radially acting tool which in addition to applying the deformation forces also must apply the preloading forces to the machine element. Accurate preloading force is necessary, for example, in rolling bearing applications which are installed without clearance or preloaded and in accordance with this prior teaching this accuracy cannot easily be obtained. Furthermore, the geometric configuration of the fastening ring is such to produce large area pressure on the relatively small contact surface which in some instances results in plastic deformation at these interengaging locations and with the result that the preloading is destroyed. For example, the machine element is in the form of a conically deformed ring which rests with a conically-shaped front face against the rounded edge of the roller bearing. Thus, with high axial preloading forces and/or with high operational axial forces, the area pressure on the relatively small contact surface has been found to be excessive and as noted above results in diminution or elimination of the preloading. The ring-like machine element is then no longer sufficiently secured or mounted in the precisely provided location to achieve the preloading and without clearance mounting of the bearing. In some instances this may lead to operational interruptions and premature failure of the bearing. Finally, these prior machine elements are thin-walled bushing-shaped rings that tend to bend as a result of the forces applied during operation and the mounting or fastening, therefore, tends to loosen. The ring may also loosen under high RPM's and resulting high centrifugal forces.
With the foregoing in mind, it is an object of the present invention to provide an arrangement for axially fastening or securing machine elements which makes it possible on the one hand to apply an accurately determined preloading to the machine element to be fastened such as the inner rings of a bearing assembly and on the other hand supports the machine element over a relatively large surface area additionally securing and accurately fastening the machine element even under the highest loads. To this end, there is provided a closed bushing-shaped ring of angular or L-shaped cross section which is adapted to be conically deformed by plastic deformation at one end thereof remote from the machine element to be fastened in such a way that the corresponding front face thereof enters in an annular groove in a shaft member or the like away from the machine element. Specifically the ring is constructed as an angular ring of L-shaped cross section wherein the radially outwardly directed leg abuts against the front fact of the machine component to be fastened and the axially extending leg portion is pressed in an annular groove in the shaft or the like at least at several circumferentially spaced locations about its periphery. By reason of the angular configuration of the ring including the radially outwardly directed leg portion, it is possible during the mounting process to apply a preload force to the machine element such as the inner rings of a double row ball bearing assembly independently of the deformation force when the preload force is applied to this leg by means of a suitable deforming tool. On the other hand, the axial end face of the radial leg portion confronting the machine element provides a large contact zone between the two and in addition stiffens or strengthens the ring and prevents in this fashion bending under high loads and consequent loosening thereof.
In order to further rigidify the mounting of the ring and prevent loosening thereof, the bore of the angular ring may be made of slightly smaller diameter than the outer diameter of the shaft on which it is mounted to produce an additional press fit.
In accordance with another feature of the present invention, the fastening arrangement additionally includes a second annular member which engages over the axial leg portion of the angular ring with a press fit. This second ring may include internal threads which cooperate and engage with threads on the shaft member located adjacent the annular groove on the shaft member or the like. When the angular ring is press fitted this arrangement contributes to maintaining the angular ring in an accurate position and at least part of the axial forces are transmitted or absorbed by the press fit. The second ring engaging over the axial leg portion may be installed by a shrink fit or the like and it serves to prevent the deformed end of the angular ring from breaking up under load and consequent loosening which is harmful to maintaining the desired preloading of the assembly.